Single doses of caffeine, in amounts within the diet of normal children, has been shown in previous studies to affect vigilance and motor activity. Currently, the subacute effects of caffeine are being examined with a group of 50 children selected for either high or low habitual dietary caffein intake. The effects of two carbohydrates, glucose and sucrose, were compared with (saccarin) placebo in a group of boys considered to have adverse behavioral responses to sugar.